1. Field of the Invention
This invention relates to a key switch assembly and, more particularly, a key switch assembly which can reliably eliminate swinging of a key end and erroneous operation due to incomplete insertion of a key.
2. Prior Art
Japanese Utility Model Publication No. 23650/1979 shows a key switch assembly, which comprises a lock body, a lock cylinder received in a lock cylinder reception bore of the lock body and having an axial key groove and a plurality of radial pin reception bores, the lock body having radial pin reception bores communicating with the pin reception bores of the lock cylinder, driven and drive pins received in the pin reception bores and biased by compression coil springs toward the key groove, a key having one edge formed with operation sections for displacing the point of contact between each driven pin and each drive pin to a position corresponding to the outer periphery of the lock cylinder, and a plurality of switches secured as an axial juxtaposition to the back of the lock body, an end portion of the key rearwardly projecting from the lock cylinder having one side provided with operation sections for depessing actuator pins of the switches and non-operation sections, through which the actuator pins can pass.
In this key switch assembly, when the key is inserted into the key groove to a predetermined depth such that its operation and non-operation sections face associated actuator pins, the point of contact between each driven pin and each drive pin is brought to a position corresponding to the outer periphery of the lock cylinder. Thus, the lock cylinder is unlocked relative to the lock body and ready to be rotated. By rotating the lock cylinder in this state with the key, the operation sections in an end portion of the key turn on or off specific switches, while the non-operation sections hold other specific switches "on" or "off". Thus, specific one of apparatuses, to which the switches are connected, are made operative, while other apparatuses are held inoperative.
With the key switch assembly having the above construction, a swing of the key end from the normal position may result in insufficient depression or failure of depression of an actuator pin of a switch, which is disposed in a deviated position. In such a case, an erroneous operation signal is possibly supplied to the associated apparatus. A major cause of occurrence of the key swing resides in the play present between the surface of the lock cylinder reception bore and the outer periphery of the lock cylinder. Therefore, it is desired to reduce the play so as to align the axis of the lock cylinder and the axis of the lock cylinder reception bore as much as possible.
However, certain allowances are provided in the manufacture of the lock body and lock cylinder, and also for smooth rotation of the lock cylinder a minimum play is necessary and indispensable. Therefore, limitations are imposed on the play reduction from the standpoints of the manufacture and functions. Further, wear produced in long use is another cause of increasing the play.
In another respect, with the prior art key switch assembly the lock cylinder is liable to be occasionally unlocked before the key is perfectly inserted to a predetermined extent. If the key is turned in this half inserted state, switches in a zone not reached by the key are not turned on or off at all, and also switches in a zone reached by the key are not turned on or off in a normal fashion, thus possibly providing erroneous operation signals to apparatuses.
In the lock structure used for this key switch assembly, a number of different key codes, i.e., key differences, are obtained by increasing or reducing the depth of each of operation section of the key and the length of each driven pin with a predetermined dimension as a unit. Actually, however, wear produced in long use is added to the allowance provided for manufacture, and it is liable that the play between the lock cylinder reception bore and lock cylinder exceeds the minimum unit of the key code setting.
To avoid the half insertion lock, the minimum unit of key code setting may be made as large as possible. When the minimum unit is increased, however, the outer diameter of the lock body and lock cylinder has to be increased to ensure a large number of key codes. This is undesired in the light of the demand for reducing the size and weight of the assembly.